>Honestly, Light isn’t all that smart. Smarter than average to be certain, but he was also incredibly arrogant which caused him to mess up a lot, such as killing Lind and Penbar, and declaring his victory at the end before he lost. His whole amnesia plan was pure luck, the chances of it working out without anything interrupting it were immensely low. I mean seriously, the dude had THE perfect murder weapon which left no forensic evidence, and because of his own stupidity and mistakes L was 90% sure it was him after a few weeks (according to the creator when L puts any probability on someone being the culprit, even just 5%, he is already around 90% sure). In any case the only reason Mello and Near were able to win in the end was because of all the groundwork laid by L, such as figuring out there was a death note and suspecting Light of being Kira in the first place. If it weren’t for that, they would have lost, so I personally choose to count L as one of the winners along with Mello and Near (though that may just be because he is my favorite character). If it came down to a straight battle of wits between Light and L, with no help from anyone or anything else mundane or supernatural, I am about 99.98% certain that L would win (once again favorite character, but come on, the dude almost managed to catch somebody who had a magic notebook that could kill people, despite not originally knowing that things like shinigami could exist).
